CVE-2015-7497 in libxml2
Summary
by MITRE
Heap-based buffer overflow in the xmlDictComputeFastQKey function in dict.c in libxml2 before 2.9.3 allows context-dependent attackers to cause a denial of service via unspecified vectors.
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Analysis
by VulDB Data Team • 06/28/2022
The vulnerability identified as CVE-2015-7497 represents a critical heap-based buffer overflow within the libxml2 library's xmlDictComputeFastQKey function located in dict.c. This flaw exists in versions prior to 2.9.3 and demonstrates the classic characteristics of memory safety issues that can be exploited to disrupt system operations. The vulnerability manifests through heap memory corruption during XML dictionary processing, specifically when handling qualified names in XML documents. The affected function processes XML qualified names and performs hash computations that can lead to unauthorized memory access patterns. Attackers can leverage this vulnerability by crafting malicious XML content that triggers the vulnerable code path, potentially causing application crashes or system instability.
The technical implementation of this vulnerability stems from inadequate bounds checking within the xmlDictComputeFastQKey function where heap memory allocation occurs without proper validation of input parameters. When processing XML documents containing specially crafted qualified names, the function attempts to compute hash keys using memory buffers that are insufficiently sized for the data being processed. This creates a scenario where memory writes can overflow into adjacent heap regions, corrupting memory structures and potentially enabling arbitrary code execution in favorable conditions. The vulnerability is classified under CWE-121 as a heap-based buffer overflow, representing a fundamental memory safety issue that violates the principle of proper memory bounds enforcement. The context-dependent nature of this vulnerability means that exploitation requires specific conditions related to XML document structure and processing context.
The operational impact of CVE-2015-7497 extends beyond simple denial of service to potentially compromise system integrity and availability. Applications utilizing libxml2 for XML processing, including web servers, database systems, and enterprise applications, become vulnerable to this attack vector. The vulnerability can be exploited through XML injection attacks where malicious actors craft XML documents designed to trigger the buffer overflow during parsing operations. In web applications, this could result in server crashes, resource exhaustion, or potentially more severe consequences if the application is configured to process untrusted XML input. The vulnerability aligns with ATT&CK technique T1203 by enabling process injection and system resource manipulation, while also supporting T1499 for service disruption and availability compromise.
Mitigation strategies for CVE-2015-7497 primarily focus on upgrading to libxml2 version 2.9.3 or later, which contains the necessary patches to address the heap overflow conditions. System administrators should prioritize patch management for all affected applications and infrastructure components that rely on libxml2 for XML processing operations. Additional defensive measures include implementing XML input validation and sanitization, restricting XML document complexity, and deploying web application firewalls that can detect and block malicious XML content. Network-level protections such as XML filtering and content inspection can provide additional layers of defense against exploitation attempts. Organizations should also consider implementing runtime monitoring and anomaly detection systems to identify potential exploitation attempts targeting this vulnerability, as the heap corruption can manifest in various ways depending on system configuration and memory layout. The vulnerability underscores the importance of maintaining up-to-date security patches and implementing comprehensive security testing practices for third-party libraries in enterprise environments.